Just Learn Code

Dynamic Coding Made Easy: An Introduction to Roslyn Scripting API

Introduction to Roslyn Scripting API

Developers that work with C# know that the language’s dynamic nature is attractive when it comes to agility and rapid programming. This is why developers need to have access to tools that help them take advantage of this feature set.

One such tool is the Roslyn Scripting API. In this article, you will learn what the Roslyn Scripting API is, how it can be used to evaluate C# expressions dynamically, and how it can be installed and configured.

What is Roslyn Scripting API? Roslyn is an open-source framework that Microsoft developed to build hosted code compilers that can be used at runtime on both .NET Core and .NET Framework platforms.

In other words, it allows developers to create programs that not only compile, but also execute code. Roslyn enables developers to access the C# analyzers and compilers to create more powerful and adaptable development environments.

The Roslyn Scripting API is a part of the Roslyn platform that allows users to evaluate C# code snippets at runtime and use them to develop interactive shell-like interfaces and console applications. This feature is achieved by allowing users to send code to a Roslyn execution engine, which evaluates the code, executes it, and sends back the result.

Purpose of Roslyn Scripting API

The Roslyn Scripting API has several use cases, making it a valuable tool for IDE developers, tool development and runtime code execution. As an IDE developer, you can use the Roslyn Scripting API to turn your IDE into a powerful interactive environment where users can write, evaluate, and modify code all within the comfort of the IDE.

Tool developers can use the API to create powerful, extensible command-line tools. Finally, the Roslyn Scripting API allows runtime code execution, which is vital in applications like serverless computing, where you want a user to be able to provide custom code to special functions at runtime.

Using the Scripting API to Evaluate C# Expressions Dynamically

Installing the API

To get started, developers must install the Roslyn Scripting API. This is done by using the NuGet package manager.

To achieve this, type the following command in the package manager console:


PM > Install-Package Microsoft.CodeAnalysis.CSharp.Scripting


Including the Library Files

After the API installation, it is important to include the library files in your code file. This is important because the API’s methods are only accessible when the project includes the proper library files.


using Microsoft.CodeAnalysis.CSharp.Scripting;


Writing the Code to Evaluate the Expression

After installing the API and including the library files, it is time to write the code that evaluates the C# expression.


var result = await CSharpScript.EvaluateAsync(“1 + 2”);



As seen from the above code snippet, the `EvaluateAsync` method is called upon by passing it string representations of C# code.

In this case, the method evaluates the expression `1 + 2` and outputs `3`.

Modifying the Code for Repeated Input and Output

One limitation of the previous code implementation is that it only permits a single input and output. To allow the user to input as many expressions as needed, we can modify the code with a `while` loop.


while (true)


var input = Console.ReadLine();

if (input == “quit”) break;



var result = await CSharpScript.EvaluateAsync(input);



catch (CompilationErrorException ex)






In the updated code implementation, we use a `while` loop to continually request input from the user and evaluate it until the user types “quit.” The input is then evaluated, and the result or `CompilationErrorException` is displayed to the user. Finally, unit testing can be done on this implementation to ensure that it meets the expected results.


In conclusion, the Roslyn Scripting API provides a powerful toolset for C# developers. With the ability to evaluate C# expressions at runtime, developers can create interactive shell-like experiences and powerful, extensible command-line tools.

This article discussed how to install and configure the Roslyn Scripting API and how to use it to evaluate C# expressions dynamically. You’ve also learned how to modify the code for repeated input and output, and how to follow up with unit testing to ensure that your program is working as expected.

In summary, the Roslyn Scripting API is a useful tool for C# developers, providing the ability to evaluate C# expressions at runtime. The API offers versatility for the creation of interactive shell-like experiences and command-line tools.

Developers can install and configure the API easily by using the NuGet package manager and the library files. The article explained how to modify the code for repeated input and output while also emphasizing the importance of unit testing to ensure that programs performance matches expectations.

With Roslyn Scripting API, developers can improve their code manipulation abilities and expedite their development processes.

Popular Posts